With a conventional bird's-eye view generation device, a bird's-eye view from immediately above the self vehicle is generated by projecting a photographed image obtained by an in-vehicle camera onto a projection plane parallel with the road surface, that is, through projection transformation with a virtual viewpoint being located perpendicularly upwards. Therefore, by displaying this bird's-eye view on a monitor, the driver's grasping of the road surface situation of the vehicle surrounding is assisted. However, with a bird's-eye view obtained through such projection transformation, there occurs signification distortion in the image for a faraway region as compared with a region nearby the in-vehicle camera, which distortion makes it difficult for the driver to obtain the sense of distance. Especially, a three-dimensional (“3D” hereinafter) object (this can be not only a human, a vehicle, but also an on-road obstacle such as a road (traffic) cone for a construction work) placed on the road surface and extending upward therefrom will be shown as a deformed shape object elongated in the photographing direction, thus presenting difficulty in visual recognition.
In order to overcome such problem as above, for example, a vehicle periphery image display system disclosed in Patent Document 1 includes a camera for photographing the vehicle periphery, an obstacle detecting means for detecting an obstacle present in the periphery of the self vehicle, a memory section for storing in advance substitute images corresponding to obstacles, and an image processing section for generating a bird's-eye view from a virtual viewpoint of the self-vehicle periphery based on an image obtained by the camera. When the obstacle detecting means detects an obstacle, the image processing section identifies this object and selects and retrieves a substitute image corresponding to the identified obstacle from the memory section and then changes the directional posture and the inclination of the selected substitute image in accordance with the virtual viewpoint and superposes this with the bird's-eye view. With this system, the image processing section converts an image obtained by the photographing means into a bird's-eye view from a upwardly or laterally of the vehicle. Then, based on the information from the obstacle detecting means, the image processing section selectively determines a substitute image corresponding to the size and movement of the 3D obstacle from the memory section and displays this substitute image in overwriting superposition on the bird's-eye view.
However, in case a substitute image is displayed in place of the obstacle image imaging the actual 3D obstacle, there can sometimes happen a situation in which the driver finds it difficult to identify the substitute image and the actual 3D obstacle. For instance, when the detected 3D obstacle is a human and an image of human represented in the form of an illustration (or an icon) or a photo is displayed, if the display screen is small, it is difficult to determine whether the human image on the display screen is identical to the actual human confirmed via a rearview mirror or the driver's eyes. Also, in case the display screen is small, it can become difficult even to recognize that the image represents a human. Moreover, if the substitute image shows a forward facing human although the actually recognized human is assuming a rearward facing directional posture, the identification becomes difficult. Further, in case a detected 3D obstacle is an automobile, if the substitute image shows a sedan facing forward although the actually recognized automobile is a minivan facing rearward, the identification becomes difficult similarly.